Before Hagel can be confirmed by the Senate, he has win the Armed Services Committee's approval. And it's not clear if Hagel, a former Nebraska Republican senator and Vietnam War hero, can overcome that first hurdle, with several Democratic and Republican panel members expressing skepticism or refusing to providing firm endorsements.

"With a wide range of challenges facing our military, I expect that Chuck Hagel's confirmation hearing will provide a forum for appropriate, insightful and frank discussions," Udall said in a statement. "If confirmed, Hagel would bring the Pentagon his remarkable experience as a combat veteran and outspoken Senate leader. I am certainly going to approach this hearing with an open mind, and I'm looking forward to discussing his vision for the future - as well as his answers to a range of critical questions."

Obama announced Hagel as his choice Monday. Critics say Hagel isn't sufficiently supportive of Israel, is soft on Iran and is cool toward gays.